Banks can't just ban you, nor just take your money. The price they pay for being gatekeepers is a ton of regulation.
This is why PayPal for the longest time made it really clear that "we are not a bank". So that they wouldn't be subject to those regulations and could suspend accounts and keep the money.
Banks can just ban you if they whisper the magic words "suspected money laundering". They are theoretically accountable to a process that takes 500 years and 3 quadrillion dollars to reach a resolution, then they will unban you. You might notice both you and the bank will be dead by that time.
> Banks can't just ban you
They kinda can.
https://www.bitsaboutmoney.com/archive/seeing-like-a-bank/